The present invention relates to an improved method for manufacturing extremely thin magnetic plates for multilayer-type head core, and more particularly relates to improvement in the mass-production of extremely thin magnetic plates for multilayer-type head cores which are advantageously used for magnetic sound recording, reproducing, magnetic video recording and reproducing.
Such alloys as sendust alloys and alperm alloys have been used as a material for magnetic head cores because of their excellent magnetic properties, appreciable hardness and high abrasion resistance. However, such materials have a serious drawback that their high conductivity results in large eddy current loss in the high frequency range and, consequently, low effective permeability when used for magnetic head cores.
In order to avoid this trouble, it has been proposed to assemble a plurality of thin magnetic plates by means of electrically insulating resins. The head core so formed has a multilayer construction in which thin magnetic plates and thin insulating layers are alternately superimposed.
The thin magnetic plates used for this purpose are in general manufactured by applying suitable machining to cast blocks. Such a conventional process for preparation of the thin magnetic plates is accompanied by serious problems as follows.
The first problem is caused by the great hardness of the sendust alloys and alperm alloys. In preparation of the thin magnetic plates, cutting is applied to the cast block so that its shape should follow that of the end product, i.e. the head core. After this cutting, the shaped cast block has to be sliced into a number of thin plates by using a suitable mechanical device such as a wire saw. This slicing process is very time-consuming due to the hard-to-work nature of these alloys.
The second problem is caused by the slicing process itself. Since the slicing is carried out by using a wire saw or the like, the portions of the cast block corresponding to the thickness of the saw have to be consumed as chips. This waste causes innegligible lowering in the yield of production.